Lighting equipment using LED elements has come into widespread use. To simplify design of lighting equipment such as desk lamps and other lighting lamps, it is common to modularize light source units. For example, FIG. 1 in a Japanese Unexamined Patent Publication No. 2009-218204 shows a light-emitting module 1 constructed by mounting a plurality of light-emitting elements 3 (packaged LED elements), a lighting circuit 4, and a connector 5 on the surface of a substrate 2 (a module substrate).
FIG. 11 is a plan view showing the surface of the light-emitting module 1 disclosed in the Japanese Unexamined Patent Publication No. 2009-218204.
The light-emitting module 1 shown in FIG. 11 comprises a disc-shaped substrate 2, and the light-emitting elements 3, lighting circuit components 4, and power supply connector 5 mounted on the substrate 2. The substrate 2 is made of aluminum formed in the shape of a disc, and has a thickness of about 1.5 mm and a diameter of about 70 mm. The upper surface 2a of the substrate 2 is a component mounting surface, and the lower surface 2b thereof provides a planar heat-sink surface. Further, an insulating layer is formed on the upper surface 2a of the substrate 2, and an interconnection pattern not shown is formed on the insulating layer.
Eight light-emitting elements 3, one spaced from another by a prescribed distance, are mounted in the center of the component mounting surface. The outer dimensions of each light-emitting element 3 are 3.5 mm square and about 1.5 mm high, and each element is a surface-mount LED element containing four LED dies. The lighting circuit components 4 are arranged along the outer periphery of the component mounting surface. The lighting circuit components 4 are components for controlling the lighting of the LED chips, and include a fuse F, a capacitor C, a rectifier REC, a voltage-regulating diode ZD, resistive elements R1 and R2, and a transistor Q. The connector 5 for connecting to utility power is located outside the array of the light-emitting elements 3. A white resist having high reflectivity is applied by printing over the component mounting surface of the substrate 2, and mounting screw holes 6 are formed at three places passing through the substrate 2.
FIG. 12 is a schematic diagram of a lighting device 10 constructed using the light-emitting module 1 disclosed in the Japanese Unexamined Patent Publication No. 2009-218204.
Since the light-emitting elements (LED elements) 3 generate heat during operation, the heat must be efficiently dissipated outside the lighting device. FIG. 4 in the Japanese Unexamined Patent Publication No. 2009-218204 shows how the light-emitting elements 3 are mounted on a heat sink (heat-sink member) 12 via the substrate 2. The lighting device 10 shown in FIG. 12 is a downlight and has a casing 11 fixedly mounted in a ceiling. The metal heat sink 12 provided with radiating fins is placed inside the casing 11, and the light-emitting module 1 equipped with a reflector 13 is mounted on the heat sink 12. The light-emitting module 1 is screwed to the casing 11 so that the heat-sink lower surface 2b of the substrate 2 is held in intimate contact with the heat sink 12 by interposing a silicone rubber sheet (not shown) therebetween. The reflector 13 is formed in the shape of a cup having a gently curved face, and its upper end has a mounting opening 13a, while its lower end provides a lighting opening 13b. 